Oscillation generator



July 15, 1924. 1,501,729

E. o. SCRIVEN OSCILLATION GENERATOR Filed July 14 1917 //4 VH for:

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Arr y Patented July 15, 1924.

UNITED STATES 1,501,729 PATENT OFFICE.

EDWARD O. SCRIVEN, OF NEW YORK, N.. Y., ASSIGNOR TO WESTERN ELECTRIC COM- PANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

OSCILLATION GENERATOR Application filed July 14, 1917. SeriaI No. 180,589.

To all whom it may concern Be it known that I, EDWARD O. Sonrvnu, a citizen of the United States, residing at New York, in the county of New York and State of New York, have invented certain new and useful Improvements in Oscillation Generators, of which the following is a full, clear, concise, and exact description.

This invention relates to improvements in oscillation enerators, and more particularly to means or preventing the transmission of oscillations of undesired frequencies.

It is well known in the art that a vacuum tube repeater of the audion type, for example, may be made to oscillate by providing a feed-back connection from the output circuit to the input circuit of the device, and by providing a condenser suitably placed in the tube circuits for tuning to the desired frequency. One type of such a generator is described by Hartley in United States Pat-.

ent 1,356,763 for oscillation generators, patented October 26, 1920.

Such an oscillator, however, for a given setting of the condenser does not produce oscillations of a single frequency, as the higher harmonics of the fundamental oscillatlons are present in appreciable intensity. If, however, a shunt is provided for the harmonics b the employment, for exam 1e, of a wave fi ter of the type described by Campbell in his United States Patent No. 1,227,113, patented May 22, 1917, or by a filtering system of the form to be hereinafter described, practically a single frequency may be derived from the generator.

If a Campbell wave filter is employed for the suppression of the harmonics, it is preferable that means, such as a high resistance, for preventing the reaction of the filter on the generator should be inserted between the filter and the output terminals of the generator, for otherwise the filter may affect the tuning of the generator or produce other objectionable distortion.

The filtering device embodied in this invention and shown herein in the form adapted to suppress the harmonics of an oscillation generator, consists of a connecting line between the generator and the outgoing line with a plurality of resistances in series in said connecting line and a plurality of capacities shunted across said line. The capacities if used should be of such values that they supply a path of low impedance to the harmonics, but a path of comparatively high impedance to the oscillations of the fundamental frequency. If the capacities are shunted by inductances to constitute tuned loop circuits, the loop circuits should preferabl be tuned to the fundamental oscillations, t ereby offering a path of very high impedance to said fundamental oscillations, but-a path of low impedance to the harmomcs.

For the better understanding of this invention, reference is made to the following description taken in connection with the accompanying drawings, in which Fig. 1 illustrates one embodiment of this invention in which a filter of one section is employed in connection with an oscillation generator.

Figure 2 illustrates an oscillation generator having a plurality of these sections. Figure 3 illustrates this invention in connection with a wave filter of the form described by Campbell in his above-mentioned patent. Figure 4 is a modified form of Fig. 2; and Figure 5 illustrates this invention in connection with a Campbell wave filter adapted to transmit to the outgoing line a certain frequency within a given band of frequencies. Each evacuated vessel in the drawings has a reference character beside it to indicate its function: thus, A indicates that the vacuum tube is an amplifier, and G indicates that the tube is an oscillation generator.-

In Fig. 1, the vacuum tube 10, taken in connection with the induction coils 11 and 12 and capacit 13, constitutes an oscillation generator of t e type described by Hartley in his above-mentioned patent. 14 is a source of voltage for said generator, its negative pole being connected to the filament 15, and its positive pole being con nected through the choke coil 16 and resistance 17 to the anode 19. shunted around the coil 11 which is connected between the filament 15 and the grid 20 is one section of the type of filtering device of this invention consisting of the resistance 22 and the capacity 23. The drop of potent al across the terminals of the capacity is impressed upon the inputterminals of anamplifier 25. The amplified oscillations in this output circuit 26 may be impressed upon other amplifiers for further amplification, or they may be, as shown, impressed by a transformer 28 upon a suitable outgoing km.

This method of associating the generator with the amplifier 25 prevents, to a considerable extent, the amplifier from receiving the harmonics of the fundamental oscillations. The drop of potential across the terminals of inductance 11 will tend to be emphasized by the harmonics, since the impedance of an inductance increases with increase in frequency. But since the impedance of a condenser decreases with increase in frequency, the condenser 23 may be chosen of such a value that it will offer considerable impedance to the fundamental 0scillations, but a relatively small impedance to its harmonics, thereby neutralizing the effect of the inductance 11. What will be impressed upon the input terminals of the amplifier will then be composed chiefly of the oscillations of the fundamental frequency, while the oscillations of higher frequency will be largely shunted through the condenser 23. Since the impedance across the inductance 11 increases with increase in frequency, there is a tendency for the voltage output of the generator to have the same variation, but this variation is prevented by the above-mentioned neutralizing effect of the capacity 23, so that approximately a constant voltage may be obtained from the generator for oscillations of widely different frequencies. Resistance 22 is inserted to prevent the capacity 23 from affecting the tuning of the oscillating circuits. It is preferable that the period of the oscillations should be determined solely by the value of the constants of the oscillatory circuit including the adjustable capacity 13. k

Condenser 30 (preferably of large capacity) is inserted to prevent the direct current from flowing through the output circuit coil 12. In order to prevent the generated oscillations from passing through that part of the output circuit containing the resistance 17 and the source of voltage 14, a choke coil 16 is inserted. The resistance 17 is of such a value that the direct current flowing therethrough is practically constant and independent of the frequency of the generated oscillations and of slight changes in the source of voltage or in the impedance between the output electrodes or other elements of the vacuum tube circuits. This enables a constant current to be derived from an oscillation generator as has been previously described and claimed by me in my United States Patent No. 1,418,739, patented June 6, 1922.

The source of voltage -14 may also be used as the output battery for the amplifier 25. This choke coil 33 is then preferably inserted to prevent the oscillating currents from passing through the battery circuit. A short circuit for the battery 14 through the primary of transformer 28 isprevented by the insertion of a condenser 27.

In Fig. 2 the adjustable condenser. 13, in-

stead of being connected between the anode 19 and the grid 20, is shown shunted around the grid circuit coil 11. The harmonic reducing device is shown to be composed of a plurality of sections, consisting of the capacities 36 to 40 inclusive and resistan' es 41 and 45 inclusive. These sections are shown to be connected to the output circuit coil 12, although they may be connected, if desired, to the input circuit coil 11, as shown in Fig. 1. The resistances 41 and 45 inclusive are shown to be connected in series in the connecting line 46, while the condensers 36 to 40 inclusive are shunted across said line. Each condenser provides an additional short circuit for the harmonics, so that the voltage across the terminals of the last condenser 40, and consequently the voltage drop across the terminals of resistance 47, is due almost entirely to the oscillations of the fundamental frequency. The voltage impressed on the amplifier 25 is supplied from the voltage drop across the resistance 47. The amount supplied may be regulated by the adjustable contact 49. The values of the resistances 41 and 45 should be such that they prevent the capacities 36 and 40 from reacting upon the oscillation tube. The capacities should be of such values that they supply a path of low impedance for the oscillations desired to be suppressed, and a path of high impedance to the frequencies desired to be transmitted;

In Fig. 3 is shown a filter of the type described by Campbell in his above-mentioned patent, which consists'of the ca acities 54 to 57 inclusive, connected in s unt to the connecting line 46 and inductances 58 to 61 inclusive in series with said line. Between this filter and the oscillation gen erator is shown a resistance 53 which prevents the filter from reacting iupon the generator 10. With such a filter practically pure oscillations are supplied to the out going line by the voltage drop across the resistance 47. The filter may be associated with the output terminals of the generator in any suitable manner. Herein it is shown connected to the input circuit coil 11.

In Fig. 4 is illustrated a generator of oscillations having a filtering device, comprising the resistances 68 to 70 in series in the connecting line 46, and tuned loop circuits 65 to 67 in shunt to saidline. These resistances prevent the tuned loop circuits from reacting upon the source of oscillations 64, which source may be an alternating current generator, or any other suitable source of oscillations'from which it is desired to transmit oscillations of a certain frequency while suppressing other frequencies. The tuned loop circuits should preferably be tuned to the frequency of the oscillations desired to be transmitted to the outgoing line. .Such being the case, they will afiord a path of 'approxlmately infinite impedance to said oscillations, while providing a path of low impedance for oscillations of different frequencies. It follows, therefore, with such a filter, that only oscillations of the desired frequency may be impressed upon the outgoing line.

In Fig. 5 a wave filter of the Campbell type CODJPIiSiIlg the tuned circuits 75 to 77 inclusive and inductances 78 to 80 is connected to the oscillation generator by the input circuit coil 11. Such a filter is adapted to transmit only a desired band of frequencies so that, providing the fundamental of the oscillations generated is within the transmitted band, the resistance 47 will impress only the fundamental oscillations upon the amplifier 25. The resistance 82 prevents the filter from reacting upon the oscillator.

Various modifications may be made in the circuit arrangements illustrated in the various figures of the drawing without departing from the spirit of this invention. The tuning condenser 13 may be connected between the grid. and anode as shown in Figs. 1 and 5, or it may be shunted across the input circuit coil as in Fig. 2, or shunted around the output circuit coil as in Fig. 3. The potentiometer shunt 47 may be inserted if it is desired to regulate the amount of energy supplied to the outgoing line, but its presence is not necessary. In Fig. 1 it has been omitted.

What is claimed is:

1. The combination with a source of oscillations, of means for suppressing the undesired oscillations from said source, and of a resistance adapted to prevent said means from reacting upon said source.

2. A source of oscillations, an inductance associated with said source, a path connected across the terminals of said inductance including means whereby the undesired oscillations from said source may be suppressed and a resistance whereby said means is prevented from reacting upon'said source.

3. An oscillation generator comprising an evacuated vessel and means for suppressing the undesired oscillations from said generator, said means being connected in series with a resistance across two of the electrodes of said vessel.

4. An oscillation generator, an inductance associated with said generator, a resistance and a capacity in series shunted across said inductance, said inductance being of such a value as to afford a path of high impedance to the desired oscillations from said source, and an outgoing line associated with said capacity, whereby only the oscillations desired are impressed upon said line.

5. In a transmission system, a wave filter comprising recurring sections each having the reactance component of its series impedance substantially negligible and the resistance component of its shunt impedance substantially negligible, an oscillation source including reactance connected to said filter to supply oscillations thereto, and means for preventing reaction of said filter upon said source.

6. In an electric transmission system, an oscillation source including reactance for determining certain characteristics of the oscillations produced, a filter connected thereto and comprising successively connected similar sections each having a tuned shunt circuit, and means including resistance in series with said source for preventing reactance of the shunt circuits from reacting upon the source ,to affect the characteristics of the oscillations produced.

7. In an electric transmission system an oscillation source, an amplifier for amplifying oscillations from said source, a wave filter connecting said source and amplifier for eliminating undesired currents produced by said source, said filter comprising like sections having shunt reactance and means including series resistance for preventing reaction of said filter upon said source.

8. In combination asource of periodic current including reactance elements for determining the frequency of the variations thereof, means including reactance connected to said source for suppressing component currents of undesired frequency produced thereby, and means for preventing the reactance of said suppressing means from affecting the frequency of the periodic current produced by said source.

9. In combination a source of periodic current including reactance elements for determining the wave form-thereof, means including reactance connected to said source for suppressing certain components of said periodic current in order to transmlt current of a desired wave form, and means for preventing the reactance of said suppressing means from affecting the waveform of the periodic current produced by said source.

10. In combination, a source of alternating current including reactance for determining certain of the characteristics of the current produced thereby, a reactive circuit and a resistance element connecting said circuit to-said source and serving to prevent pression means for preventing reaction of said suppression means upon said source.

12. In combination, an electrical oscillator having variable reactance whereby said lib.

oscillator may be adjusted to produce oscillations of any one of a plurality of frequencies, the amplitude of said oscillations varying with frequency, a work circuit to which said oscillations are to be supplied, and means interposed between said oscilla tor and said work circuit for transmitting said oscillations therebetween and responsive to said oscillations for maintaining the oscillations transmitted to said work circuit at substantially the same amplitude at said different frequencies.

13. In combination, adjustable means for producing electrical waves of any one of a plurality of different frequencies, said means tending to produce a greater output when adjusted to certain. frequencies than when adjusted to other frequencies, a Work circuit connected to said wave producing means, and means responsive to said output waves for equalizing their magnitudes comprising a large resistance element connected' in series between said wave producing means and said Work circuit, and at capacity element shunted across said work circuit.

14. In an oscillation generator, am amplifying device having an input and a divided output circuit, means to couple said input and output circuits to produce oscillations, a source of energy for said divided output circuit connected in one path thereof, means in said path to prevent the flow of generated oscillations therein, and a re.- sistance in the other path to determine the amplitude of the generated oscillations.

15. In an oscillation generator, a thermionic vacuum tube amplifying device having an input "and a divided output circuit, means to couple said input and output circuits to produce oscillations, a source of energy for said divided output circuit connected in one path thereof, means in said path to prevent, the flow of generated oscillations therein, and a resistance in the other path to determine the amplitude of the generated oscillations.

16. In an oscillation generator, an elec tricdischarge device having an anode, a. cathode and an impedance controlling element, an input circuit for said tube comprising said impe'dance controlling element and cathode, an output circuit for said tube comprising said anode and said cathode, means to couple said input and output circuits to produce oscillations, a source of energy for said divided output circuit connected in one path thereof, means in said path to prevent the flow of generated. oscillations therein, and a resistance in the other path to determine the amplitude of the generated oscillations.

In witness whereof I hereunto subscribe my name this 13th day of July, A. D. 1917.

EDWARD O. SCRIVEN. 

